Method and apparatus for removing combustion chamber deposits



Y H. w. SIGWORTH ETAL 2,843,645

METHOD AND APPARATUS FOR REMOVING A COMBUSTIONCHAMBER DEPOSITS OriginalFiled June 29, 1953 4 Sheets-Sheet 1 TOP DEAD CENTER I PISTON TRAVELBOTTOM DEAD CENTER CRANKSHAF'T {DEGREES I NORMAL OF ROTATION 1-IGNITIONOPEN EXHAUST VALVE MOTION INTAKE VALVE MOTION INVENTORS HARRISON wS/GWORTH EDWARD J. McLAUGHL/N 44 g 6'. g g,

ATTORNEYS July 15, 1958 H. w. SIGWORTH ET AL 2,843,645

METHOD AND APPARATUS FOR REMOVING COMBUSTION CHAMBER DEPOSITS OriginalFiled June 29, 1953 4 Sheets-Sheet 2 F|G.3A FIG-.3-B

INVENTORS HARRISON W S/GWORTH EDWARD J. McLAUGHL/N 'a/QWL ATTORNEYS July15,1958 H. w. SIGWORTH ETAL 2,843,645

METHOD AND APPARATUS FOR REMOVING COMBUSTION CHAMBER DEPOSITS OriginalFiled June 29, 1953 4 Sheets-Sheet 3 5 FIG.5

INVENTORS' HARRISON w S/GWORTH EDWARD J. McLAUGHL/N Z 44%; a ATTORNEYSJuly 15, 1958 H. w. SIGWORTH ET AL 2,843,645

METHOD AND APPARATUS FOR REMOVING CQMBUSTION CHAMBER DEPOSITS OriginalFiled June 29. 1953 4 Sheets-Sheet 4 1 SPARK PLUGS NODUUI- FIG.6

INVENTORS HARR/SON w S/GWORTH EDWARD J. McLAUGHL/N' M BY 7 5 1 awuo.

ATTORNEYS- METHOD AND APPARATUS F03 G COMBUSTIUN (IHAMEBER DEPUSETSOriginal application June 29, 1953, Serial No. 364,796. Divided and thisapplication August 30, 1957, Serial No. 681,217

4 Claims. (Cl. US -14.8)

The present invention relates to methods of removing deposits fromcombustion chambers of internal combustion engines, more particularly tomethods of removing combustion chamber deposits from the combustionchambers of operating spark-ignition internal combustion engines, andhas for an object the provision of methods and apparatus for removingcombustion chamber deposits by radically advancing the spark of aspark-ignition engine during operation thereof in order to increase thep wer output and decrease the octane requirement without removal of thecylinder heads of the engines.

This case is a division of our co-pending application Serial No.364,796, filed lune 29, 1953,'entitled Methd and Apparatus for RemovingCombustion Chamber Deposits.

In the operation of high-compression internal combustion engines of thesparloignition type, such as those used in present-day automobiles,buses, trucks and boats, a commonly observed phenomenon after a fewhours of operation is an increase in octane requirement and anaccompanying decrease in power resulting from the accumulation ofdeposits in the combustion chambers of the engine. These deposits resultfrom the burning of gasolines, especially those containing tetraethyllead as an anti-knock agent, and a small amount of lubricating oil inthe combustion chambers of the engine under normal operating conditions.Primarily these deposits are composed of carbon .and lead, but,additionally, they may contain minor percentages of other materials,such as metals from the lubricating oil compounding, hydrogen, sulfur,chlorine, bromine, silicon and iron.

In recent years, designers and manufacturers of sparkignition, internalcombustion engines have found it advantageous to increase thecompression ratios in order to increase engine efficiencies. However,with increased compression ratios there is an accompanying increase inoctane requirement when the engine is clean, and under normal operatingconditions the octane requirement of the engine progressively increasesto an equilibrium requirement several octane numbers higher than theoriginal, clean, requirement due to the above-mentioned combustionchamber deposits. In present-day commercial practice, this increase inoctane requirement may easily increase sufficiently so that the enginecannot be operated Without knock on commercially available fuels undersome operating conditions.

It has been found experimentally that the octane requirement of anautomobile engine increases from a clean condition to an equilibriumcondition by about 4 to 15 octane numbers, with an average of about 8numbers, as a result of build-up of combustion chamber deposits. Suchincreases will, of course, depend upon the design of the engine, and thetime required for the build-up will depend upon the operating conditionsunder which the engine is run. It has been estimated that the annualcost to the petroleum industry of raising the octane level of all motorgasolines by one number is several million States Patent 0 dollars. forautomobile engines by a similar amount would represent a correspondingsaving to the industry and ultimately the automobile operator. Thissaving is in the cost of Octane numbers alone and without regard to thepower loss of 4 to 20% which normally accompanies a build-up ofcombustion chamber deposits.

The power increase accompanying a reduction in octane requirementrepresents an additional advantage which would accrue to the operator ofthe equipment employing a spark-ignition engine.

Heretofore, one of the most eifective methods of re moving deposits fromcombustion chambers of an internal combustion engine included removal ofthe cylinder head of the engine. Such an operation is very expensive intime and money so that it can often be justified only when overhaul orrepair of the engine is re quired. This is particularly true ofvalve-in-head engines wherein more of the engine must be disassembled toreach the combustion chambers.

Other methods have been suggested for removing combustion chamberdeposits, such as the introduction of rice or walnut shells, using anair-blast. The disadvantages of these methods reside in the length oftime required for effective carbon removal from all cylinders and highcost of necessary air-blast equipment.

Another method suggested for cleaning the combustion chambers of aninternal combustion engine is disclosed in the patent application ofJohn G. Mingle, lr., Serial No. 203,220, filed December 28, 1950, forRemoval of Combustion-Chamber Deposits in Spark ignition Engines,assigned to the assignee of the present invention, now abandoned. Asdisclosed therein, fuels other than tank fuel are introduced into theintake manifold of the engine and the engine operated for apredetermined time. While the method of the above-identified applicationis highly successful in removing combustion chamber deposits, thismethod requires the introduction of particular materials as fuel for theengine.

In accordance with the present invention, there is provided a method ofremoving combustion chamber deposits from each cylinder of an operatingspark-ignition internal combustion engine while operating the engine ontank or normal fuel by radically advancing the spark to each cylinder sothat substantially all of the combustible mixture normally drawn intoeach combustion chamber is burned while the piston associated therewithis on the compression stroke, and then maintaining the hot combustionproducts from the burned mixture in the chamber during the power strokeof the piston.

In a preferred method of carrying out the present invention, thecombustible mixture in each cylinder is ignited at a point between about10 degrees before bottom dead center on the intake stroke of the pistonassociated with the chamber and 45 degrees before normal spark ignitionof the combustible mixture. The angles referred to hereinabove aremeasured by the rotation of the crank shaft driven by the pistonsassociated with the respective chambers of the engine. The burningmixture and the combustion products are maintained in the enginecombustion chamber during both a substantial part of the compressionstroke and the following power stroke. Desirably the method includesoperating the engine at substantially full throttle without externalload on the englue and for a period of time such that the coolant forthe engine does not exceed its boiling point temperature.

While various forms of apparatus will be disclosed hereinafter forcarrying out the method of the present invention, a preferred form ofapparatus for performing the method includes a novel form of ignitiondistributor rotor suitable for use in a normal distributor for aninternal combustion engine. Said apparatus includes a Conversely, areduction in octane requirement nonconductive body adapted to be driven,a contact member supported by the body and adapted to engage the centralcontact of a normal distributor cap. A first spark-gap electrode issupported by the body and connected to the contact member to provide anelectrical path to the equally spaced terminals in the distributor cap.A second spark-gap electrode forming an electrically conducting path isangularly displaced from the first sparkgap electrode with means beingprovided for connecting the second electrode to the central contact andsaid second spark-gap electrode forming a spark-gap of lesser dimensionswith the terminals of the cap than the first spark-gap electrode whensaid rotor is operated above a predeterminable minimum speed ofrotation.

Further objects and advantages of the present invention will becomeapparent from the following detailed description taken in conjunctionwith the accompanying drawings.

In the drawings,

Fig. l is a composite graph illustrating the relationships between thefour cycles of a spark-ignition internal combustion engine and theoperation of the intake and exhaust valves.

Figs. 2A and 2B illustrate the two operating con ditions of adistributor rotor constructed in accordance with the preferred form ofapparatus for carrying out the present invention.

Figs. 3-A and 3B are illustrations of an alternative form of distributorrotor suitable for performing the method of the present invention andillustrating the two operating conditions for the rotor.

Fig. 4 is a schematic representation of another form of apparatus forcarrying out the method of the present invention which includes anindependent spark-ignition source including a vibrator.

Fig. 5 is a schematic representation of another form of apparatus forperforming the method of the invention and particularly illustrates anapparatus for rotation of a distributor cap.

Fig. 6 is a schematic representation of another form of apparatus forcarrying out the method and includes means for switching simultaneouslyeach of the spark plug leads connected to a distributor.

Referring noW to the drawings, and in particular to Fig. 1, it will beobserved that the piston travel has been plotted against crank shaftdegrees of rotation, with the individual strokes of the piston in thecombustion chamber with which it is associated identified as exhaust,intake, compression and power. The abovedescribed plot of piston travelidentifies in general the movement of a piston associated with thecombustion chamber during its four strokes in a spark-ignition engine towhich the present invention may be applied. It will be apparent to thoseskilled in the art that the present invention may be effectively appliedwith equal advantage to a two-stroke cycle spark-ignition engine.

As stated hereinbefore, the present invention is directed to the methodof removing combustion chamber deposits accumulated in an internalcombustion engine during normal operation thereof by radically advancingthe spark ahead of the point in the piston travel at which thecombustible mixture would be ignited normally. The normal ignition pointhas been identified as a band of approximately 45 degrees width ahead oftop dead center when the piston is between the compression and powerstrokes.

In order to explain the reason for this normal ignition being identifiedas a band of this width, it will be desirable at this point to explainthe advances in spark which occur during normal operation of aspark-ignition, high-compression engine. In general, these sparkadvances are present as a result of three individual advances Which arepresent in varying degree dependent upon the operating condition of theengine. The first of these advances is that due to basic timing asrecommended by the manufacturer of the engine. This advance may be inthe order of O to 5 degrees ahead of top dead center and is normallyadjusted with the engine idling at about 300 to 500 R. P. M. The secondadvance normally present in high-compression spark-ignition engines isintroduced by a centrifugal advance mechanism present in thedistributor. This centrifugal advance mechanism is constructed so that,upon increase in speed of the engine and the distributor, the spark isnormally advanced from about 5 to 15 degrees over and above the basicspark advance. The third spark advance normally present inhiglrcompression spark-ignition engines is introduced by the vacuum ofthe intake manifold. This advance may be in the range of 15 to 20degrees when the engine is operated at part throttle. In normalcominerciai construction of most automobile engines, this vacuum advanceof the spark ignition is entirely cut out by full throttle operation ofthe engine at low speeds. In some engines, such as those used in latemodel Ford automobiles, spark advance is determined entirely by vacuumsproduced in the venturi section of the carburetor and the intakemanifold, without the use of mechanical centrifugal advance.

From the foregoing description it will be appreciated that normalignition will depend upon the speed and operating condition of theengine and may occur up to about 45 degrees before top dead center inthe travel of the piston. In the operation of some very high-speeengines, the spark advance may be advanced to an even greater degree,since time is required for burning the mixture. Under high-speedoperating conditions, this may require ignition of the fuel-air mixtureat a much earlier time in order that maximum power may be obtained.

Accordingly, it will be understood that the portion of the graph in Fig.1 identified as normal ignition will be of varying width but in generalWill be equivalent to 45 degrees or less of crank shaft rotation. Inaccordance with the present invention, we have found that by ignitingthe combustible mixture normally drawn into a combustion chamber whilethe engine is operating on tank fuel at a time earlier than said normalignition, it is possible to obtain destruction of the combustion chamberdeposits in a highly effective manner. The exact point in the rotationof the crank shaft at which the combustible mixture is ignited isidentified in the graph as that portion identified as purge ignition. Wehave found that such purge ignition may occur at a point several degreesahead of bottom dead center while the piston is on the intake stroke. Ingeneral, this point is limited only by the intake stroke beingsufficiently completed to draw into the chamber the combustible mixtureand the intake valve being less than completely open. Specifically, theignition may occur as early as 10 degrees of crank shaft rotation beforebottom dead center on the intake stroke of the piston.

We are not fully aware of the mechanism by which combustion chamberdeposits are removed by radically advancing the spark. However, we havefound that when said spark is made to occur Within the range identifiedas purge ignition on the graph in Fig. l, destruction of the depositoccurs and we believe that this may result because of thermal shock andburning of said deposits which is induced by initiating the burning ofthe fuel-air mixture in the combustion chamber while the piston is onthe compression stroke and then maintaining the combustion products inthe combustion chamber during the power stroke of the engine.

In experimental runs with an internal combustion engine operated inaccordance with the present invention, we have found that it is possibleto reduce the octane requirement of an engine to within one octanenumber of the cleaned requirement of that engine. As stated hereinabove,the physical and chemical reactions which result in the destruction ofcombustion chamber deposits by operating of an engine in accordance withthe invention are not fully known, and accordingly the invention is notlimited to the correctness of the theory expounded above.

In the preferred form of the invention, the method of removingcombustion chamber deposits is carried out by advancing the ignition ofthe individual cylinders in an operating spark-ignition engine after theengine has been started and run with normal ignition during a warm-upperiod. The ignition is then advanced into the range of purge ignition,as described in Fig. 1 and the engine operated at full throttle for aperiod of about three minutes. Maximum obtainable speeds under purgeoperating conditions are in the neighborhood of about 3000 R. P. M. evenwith no external load, because of the large amount of power required tocompress the burning mixture in the combustion chambers. Sometimes thecoolant in the water jacket of the engine approaches the boiling pointduring purging. Such boiling is induced by the greatly increased heatingeffect induced by com pressing a burning mixture of the fuel and air andthen maintaining that burning and the combustion products within thechamber until the normal opening of the exhaust valve. The relationshipbetween the opening and closing of the exhaust and intake valves for atypical engine is indicated in the lower portion of the graph, Fig. 1.

While various forms of apparatus may be used to perform the method ofthe present invention, several of which will be described in connectionwith the remaining figures of the drawings, there is illustrated inFigs. 2-A and 2-3, and an alternative form thereof in Figs. 3A and 3-3,novel apparatus to permit normal starting and idling of the engine whichis further adapted to advance radically the spark ignition of an engine.As particularly shown in Figs. 2-A and 2-B, this apparatus comprises anovel construction for an ignition distributor rotor 20 having anonconducting body 21 provided with a normal or first electrode 22adapted to make electrical connection during starting and idling of theengine with a row of equally spaced terminals 23 in the distributor cap.These terminals are normally connected to the spark plugs of the engine.In addition to the first electrode arm 22, which is connected throughbar 24 to a central contact 25 adapted to engage the central contact ofthe distributor cap, rotor 20 is provided with a second spark-gapelectrode arm 26 supported by body 21 and connected to the centralcontact member 25 through bar 27. As particularly shown in Fig. 2-B,second electrode arm 26 is movable outwardly by centrifugal force fromthe position illustrated in Fig. 2-A to that shown in Fig. 2B. The speedat which such centrifugal force, due to rotation of rotor 20, occurswill, of course, be determined by the design of the leaf spring materialfrom which arm 26 is constructed with the spring tension of arm 26 beingselected to effect purging at engine speeds above about 1500 R. P. M.Arm 26 will attain the position illustrated in Fig. 2-13 so that thecontact 28 approaches the row of terminals 23 at a distance d2, which isless than the normal spacing between the first electrode and the row ofterminals identified as d1. Movable arm 26 is guided in its motion andlimited in its radial movement by a fixed member 29 adapted to engage aslot formed in electrode arm 26.

In the operation of the rotor illustrated in Figs. 2-A and 2B, theengine may be started and idled with the distributor rotor operated asshown in Fig. 2A, thereby permitting each of the electrodes 23 to beenergized by first electrode 22 and thus provide normal ignition for theengine. Upon increase in the speed of the engine, movable arm 26 isforced outwardly into the position shown in Fig. 2-3 and therebyprovides a preferential path to the electrodes, which, in the presentinstance,

are so arranged that each spark plug is energized oneeighth of a cycleearlier than would normally be its time of ignition. Accordingly, thereis provided in a normal four-stroke-cycle engine having eight cylindersan ad- Vance of degrees in the timing of the ignition. This 90-degrceadvance is, of course, over and above the normal advances present in theengine for the speed and other operating conditions of that engine.

An alternative arrangement for radically advancing the spark inaccordance with the method of the present invention by a justment of therotor of the distributor is shown 3-A and 3B. in that arrangement thesecond electrode 26A is mounted on body 21 and has a fixed relationshipbetween the contact end thereof 28A and the fixed row of terminals inthe distributor cap. However, the second electrode 26A is notpermanently connected to central contact 25 of the rotor body but,rather, is connected thereto by a movable contact means which issubjected to centrifugal force and closes the contacts at the inner endof bar 26A and the outer end of movable arm 3d. These contacts areidentified as 31 and 32, respectively. The operation of the arrangementof Figs. 3-A and 3-13 is believed self-evident from the abovedescription and serves to provide a preferential path to the row ofspark plug terminals 23 of width d2 when rotor body 21 is rotated abovea predeterminable minimum speed. The arm 26A in the arrangement of Figs.3 A and 3-B has a fixed angular relationship to the first electrode 22such that the spark for each cylinder may be advanced one-eighth of thetwo revolutions, or 90 degrees ahead of its normal sparking time.

Referring now to Fig. 4, there is illustrated another form of apparatussuitable for carrying out the method of the present invention. In thearrangement of Fig. 4 there is illustrated schematically the normalspark-ignition system, including a distributor 4,4 for a six-cylinderengine indicated generally by the cylinders numbered 1 to 6, inclusive,each of which is provided with a spark plug 41. As will be understood bythose skilled in the art, the basic timing of the spark appearing atspark plugs 41 is controlled by the position of cam and breaker assembly42 driven as indicated schematically by dashed line 43 by the cam shafti-i and timing chain 45 from the crank shaft in normal operation,opening and closing of switch 48 of cam and breaker assembly 42 produce,by means of induction coil 5d, a high voltage in line 49, which istransmitted to distributor rotor 5'1. As further shown, the normalignition system for the engine includes a condenser 47 in parallel withthe switch 4-3 and an ignition switch 52 for connecting the battery 53or generator (not shown) to the primary of coil 5%.

As stated above, the normal timing of the engine is under the control ofcam and breaker assembly 42, and so long as the distributor rotor issubstantially closer to one of the terminal electrodes than to anotherelectrode at the time the switch makes and breaks its Contact, thepotential induced by coil 5h in line 49 will permit proper firing of thecorresponding cylinder to burn the fuel-air mixture during the powerstroke.

in accordance with the present invention, there is provided, in additionto the normal spark-ignition system, a means for introducing a highpotential through line 4-9 which is both continuously available and ofhigh he quency. in the present instance, this independent source of highpotential is generated by auxiliary coil 60 having vibrator arm 61,which is intermittently opened and closed at any predeterminable rate bythe action of the core of coil dtl on switch arm 63.. Switch arm 61 isarranged to connect the primary st of coil 6d to a potentia' source inded as battery as through switch 64. A continuous h n potential is indu.d in secondary winding 65 by the making and breaking of vibrator arm61, and this high potential may be applied to line and distributor 5through switch 57.

In the operation of the arrangement of Fig. 4, the rotating electrode 68may have continuously applied thereto the potential generated byauxiliary coil 60 so that, upon normal rotation of rotor 51, the sparkfrom the end of electrode 68 will continuously arc to the nearest ofeither of two electrodes 69, between which it is then located. Forexample, with rotor 51 turning in the direction indicated by the arrow,electrode 68, when in the dotted position shown in the drawing, willpreferentially jump to the terminal connected to the No. 6 cylinderrather than to the No. 3 cylinder when the circumferential distance 71becomes slightly less than the circumferential distance 70. Accordingly,it will be seen that an advance of one-twelfth of the normal tworevolutions of rotation of the crank shaft may be achieved in asix-cylinder engine of the type shown in Fig. 4. Accordingly, there maybe produced 60 degrees of spark advance over and above the normal sparkadvance of the engine operating at a particular speed and load by thearrangement shown in Pig. 4. In accordance with another aspect of thepresent inven tion, the arrangement of Figs. 2-A and 2B, as well asthose of Figs. 3A and 3-B may be combined with the spark advance methoddisclosed in Fig. 4 to obtain additional advance in the spark of thecombustion chamber to produce a more radical spark advance. For example,in a six-cylinder engine, the spark advance obtained by the combinationof the arrangement of Fig. 4 with the rotors disclosed in Figs. 2 and 3will produce an advance of 180 degrees ahead of normal spark ignitionfor the engine; and, in an eight-cylinder engine, the correspondingadvance will be 135 degrees.

Referring now to the arrangement of Fig. 5, there is shown analternative arrangement for advancing the spark which is particularlyuseful for periodic purging of combustion chamber deposits duringoperation of an internal combustion engine such as those used inautomobiles. In the arrangement of Fig. 5 a rack and pinion arrangement66 is adapted to rotate the cap, or alternatively the body, of adistributor by a predeterminable amount by energization of solenoid 77through depression of a push button 72. The push button 72 may beconveniently located on the instrument panel 73 in the operatingcompartment of the automobile. Adjustment of the movement of degrees ofadvance by the energization of solenoid 77 may be conveniently providedby adjustment of stop nut 74 on the end of rod 75 and thereby limit thenumber of degrees of rotation of the distributor 7 6 by rack and pinionarrangement 66.

Referring now to the arrangement of Fig. 6, it will be seen that aswitching mechanism, identified generally as 80, may be provided forswitching simultaneously the leads from a distributor cap 81 to theindividual spark plug leads identified as 82. It will be seen in Fig. 6that the operating coil 84 may be energized by battery 85 through pushbutton 86.

In the operation of the arrangement of Fig. 6, switch 89 may beenergized after the engine has been started and idled for a particularperiod of time, and the spark ignition may be advanced in each of thecylinders of the operating engine by at least the interval between theterminals in the cap of the distributor. In the arrangement of Fig. 6this advance amounts to one-sixth of two revolutions, or 120 degrees.

In addition to the apparatus described in connection with Figs. 2 to 6,inclusive, additional means may be utilized for advancing the spark inmanner to perform the method of the present invention. Among thesemethods is that of rotating the body of the distributor after the enginehas been started.

Another method for inducing radical advance of the spark may include theintroduction of oxidizable particles of the order of about 200 to 300mesh, such as carbon, and carbon-containing particles whose oxidation iscatalyzed by metals such as lead, copper, and calcium, through theinduction system of the engine. It has been found that by suchintroduction of particles to the combustion chamber, such particles maybe brought to incandescence during a normal ignition and burning of thefuel-air mixture and the particles retained in the combustion chambersduring the subsequent exhaust and intake strokes of the engine and theninduce ignition of the fuel-air mixture during the compression strokeand at a time sutficiently early to cause destruction of the combustionchamber deposits present in the engine cylinder.

From the foregoing description of the various forms ofapparatus andmeans for producing a radical advance in the spark ignition of anoperating internal combustion engine, it will be appreciated that themethod broadly comprehends the steps of igniting the fuel-air mixture inthe combustion chambers of an operating engine during the compressionstroke and maintaining the combustion products in the engine cylinderuntil the exhaust valve opens. In this way the burning mixture and thecombustion products are held in the combustion chamber for about 225degrees to 370 degrees of crank shaft rotation. By such abnormalincrease in the operating temperature of the combustion chamber byvirtue of the present invention, the temperature of the depositsaccumulated in the chamber during normal engine operation is raisedsufliciently to cause burning and volatilization of the deposits. Thesetemperatures are in part attained by continuation of the operation ofthe cylinder through a large number of cycles of preignition ofpredeterminable amount. Accordingly, it will be understood that removalof the deposits is achieved only by repetitive preignition rather thanby sporadic or occasional preignition as may be encountered in normalengine operation.

Various modifications and changes in the method and apparatus forcarrying out the present invention will become apparent to those skilledin the art from the foregoing description. All such modifications andchanges which fall within the scope of the appended claims are intendedto be included therein.

We claim:

I. An ignition distributor rotor having a nonconductive body adapted tobe connected with a driving shaft, a contact member supported by saidbody and adapted to engage the central contact of a distributor cap,said cap having a row of equally spaced terminals for connection withspark plugs, a first spark gap electrode supported by said body andconnected with the contact, said first electrode extending beyond therotor body to form an electrically conductive path to said row ofterminals, a second spark gap electrode supported by said body, saidsecond electrode forming an electrically conductive path extendingoutwardly from said body and angularly displaced from said first sparkgap electrode, and means for connecting said second electrode to saidcontact, said second spark gap electrode forming spark gap of lesserdimensions with each of the terminals of said row of terminals than thespark gap between said first spark gap electrode and said terminals whensaid rotor is operated above a predeterminable speed of rotation.

2. A rotor for a distributor of a spark-ignition, in ternal combustionengine comprising a rotatable, nonconductive body, contact meanssupported by said body and adapted to engage the central contact of adistributor cap having a row of terminals for connection with the sparkplugs of said engine, a first spark gap electrode means supported bysaid body and in electrical connection with said contact means, and asecond spark gap electrode means including an electrode member formingan electrically conductive path supported at its inner end by said rotorbody and means responsive to centrifugal force produced by rotation ofsaid body for energizing the gap between the outer end of said electrodemember and said row of terminals in said cap.

3. A rotor in accordance with claim 2, in which said electrode memberhas a fixed radial length greater than the radial length of said firstspark gap electrode means and said means responsive to centrifugal forceincludes a contact arm electrically connected to said contact meansmovable into engagement with said electrode member.

4. A rotor in accordance with claim 2, in which the outer end of saidelectrode member is movable radially and said means responsive tocentrifugal force includes 10 means for limiting the radial movement ofsaid electrode member for predetermining the position of said outer endcloser to said row of terminals than said first spark gap electrodemeans.

No references cited.

